Pneumatic-despatch-tube apparatus



' J. G. MACLAREN.

PNEUMATIC DESPATOH TUBE APPARATUS.

APPLICATION FILED AuG.25. I917.

1,367,163. Patented Feb. 1,1921.

4 SHEETS-SHEET I.

Inventor. clams (2. Maclaren,

1. G. MACLAREN. PNEUMATIC DESPATCH TUBE APPARATUS. PPLICATlON FILED AUG-25, I9I7.

1,367,163. Patented Feb. 1, 1921.

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clams (Z.Mac,lai-en,

I a0 a7 J. G. MACLAREN.

PNEUMATIC DESPATCH TUBE-APPARATUS APPLICATION HLED Aumzs. 19:7.

Patented Feb. 1, 1921.

4 SHEETS-SHEET 3.

James (2. Mach e,

by M tilys.

APPLlCATlON F iLED AUG 25, 19!].

Patented Feb. 1,1921.

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JAMES G. MAGLAREN, 0h MAMARONECK, NEW YORK.

i PNEUMATIC-DESPATCH-TUBE APIBARATUS.

Specification of Letters Patent.

Patented Feb. 1, 1921.

Application filed August 25,1917. Serial No. 188,185.

despatch tube apparatus and is more especially, though not necessarily exclusively concerned with a system of the class in which a single transit tube is utilised for the transmission of carriers in opposite directions, and in which air under a pressure above that of the atmosphere, is admitted to the transit tube for the propulsion of the carriers.

My invention will be best understood by reference to the following description when taken in connection with the accompanying drawings of two specific embodiments there off, while its scope will be more particularly pointed out in the appended claims.

In the drawings:

Figure 1 is an elevation, partly in vertical section and partly broken away, ot a pneumatic despatch tube apparatus embodying my invention; 1 i

Fig. 2 is a plan, on an enlarged scale, cit one ot the terminals; r

Fig. 3 is a sectional view on line of 2, showing the parts in therelative positions which they normally occupy;

Fig. l is a sectional view similar to Fig.

3., but showing the parts in a position which they occupy during the transmission of a carrier from the terminal there represented;

Fig. 5 is a detail sectional view on line 5-501 Fig. 41;;

Fig. 6 is a sectional view on line 6-l3 of Fig. 1;

Fig. 7 is a plan oi another form of termi nul eml'iodying my invention;

Fig. 8 is a sectional view on line 8-8 0t Fig. 9 is a detailsectional view on line 99 of Fig.7, and i 10 is a detail sectional view of a modification of the timing means.

Referring to Figs. 1 to 6 inclusive, and to the embodiment of my invention which is illustrated therein, I have there shown a pneumatic despatch tube apparatus comprising a translt tube 11 connectlng two terninals 12, which may be and are herein identical in construction, though one is arranged for upward and the other downward discharge of carriers. Each of these termi nals is herein equipped with a chute 13 of usual construction to check the speed of the emerging carrier and to assist in bringing the latter to rest at a suitable point. As a means for supplying an air current for the propulsion of the carriers through the transit tube,

I have herein provided a motor driven air compressor it which delivers compressed air through a pipe 15 to a receiver or storage tank 16,110111 whence branch pipes 17 lead to the respective terminals 12. Since the latter are herein 0t ldentlcal construction, a

detailed description of one will sutlice for both. i i y i 1 Referring now more particularly to Figs. 2 to 6 inclusive, the terminal 12 is provided with a chamber 18 communicating in any suitablctmanner with the transit tube 11, the

latter for this purpose being herein provided with one or more perforations 19. Comnumicationbetween the air supply pipe 17 and the transittube 11 may be controlled by any suitable valve, such for example as a valve 20 hereinafter called the air inlet valve, "the latter cooperating with a suitable seat 21 and having a stem 22 mounted to slide vertically in a guide 23. Any suitable means .may be provided for normally holding the valve 20 seated, but herein I have provided a helical spring 2 1 encircling the valve stem within the guide 23, and serving in an obvious manner to assist the air pressure in holding the valve seated except when itis purposely opened,

its a means l'or closing the carrier inlet and outlet or the transit tube, I have herein provided a suitable closure 25 sometimes called a door, of common form, usually made of leather or some other suitable more or yielding material, secured. to a Iitillk Ltorcing platc 26 and carried by a lever 27. As a means for attaching the door to the lever I have herein provided a bolt 28 passing through both, and encircling this bolt is a suitable spring 29 interposed between the plate 26 and the lever 27 and constantly tending to move the door 25 away fromthe lever 27 for purposes which will presently appear.

The door carrying lever 27 is herein fulcrumed on a pivotal pin 30, and is interposed between a pair of ears 31. its a means for normally holding the door open and automatically returningit to its open position after having been closed, I may provide any suitable means, such as a spring 32, although in the case or" a downward discharging terminal this spring may be omitted it desired and gravityalone relied upon to open the door. 'Any suitable type of spring may be employed for this purpose, but herein the latter is helically coiled about a rod 33, and isinterposed between two abutments 34 and 35, one otwhich is mounted in lined posi: tion on saidrod, while the other is mounted to slide for a purpose which will presently appear. 'ierein the rod 33 is pivotally connected to the lever 27 by a pivotal pin 36 andextends loosely through a perforation 37 ina plate 38, the latter constituting the top or cover plate of the terminal 12, and being secured in place above the chamber 18 by a plurality of screws The abutment-34 may be,and is herein, mounted to rock with relation to the top plate 38, and

for this purpose is herein provide with a pair of V shaped projections 40, resting in shallow grooves in the underside of the plate and acting as a fulcrum resembling that of a scale-beam. it will be evident that, when the lever 27 is swung about the axis of its pivot 30, the axis of the pivot 36 will describe an arc ot'a circle, and hence the rod 33 will be swung back and forth about the knife edge projections 40 as a fulcrum. Any suitable means may be provided for limiting the opening movement of the door. 25, but herein the rod 33 is provided with an abutment 41 adapted to engage the upper side of the plate 38, asshown in Fig. 3. V

Theinlet valve 20 is preferably under the a control out the described .mechanism for closing the transit tube. This control may be efl'ected by other means, but in the example illustrated in Figs. 1 to 6 inclusive, I have provided a plunger 42 mounted to slide vertically in an upper guide 43 and a lower 7 guide 44, and suitablyconnected t0 the valve stem'22 as by means of a lever 45 pivoted at 46 and having a forked or bifurcated end 47 which embraces the plun er and is held against a shoulder or collar 48, on the la ter by means of the spring 24 hereinbefore described. The lower end of the guide 44 may be provided'with a vent ort 49 to provide for the free entrance and escape of air to and from the space beneath the plun- .ger .42, thereby to permit freedom of action of the latter. The plunger 42 may be actuated by the closure mechanism in any suitable manner, but herein the lever 27 is provided with a plate 50, which, during the closing movement of the door 25, is adapted to engage the upper end of the plunger 42, thereby to depress the latter and to open the air inlet valve 20 in opposition to the spring hen this occurs, the compressed air from the supply pipe I7 is admitted into the chamber 18, and passes therefrom through the openings 19 into the despatch tube 11. thereby propelling a previously inserted carrier to its destination.

Any suitable form of latching or locking means may be emoloyed, but herein I have provided a latch in the form of; a lever 51 mounted on a pivot 52, and having an arm adapted engage the upper side ol the plate (:0, as shown in Fig. 1-. ll hen the latch is moved into and held in this position by sui' .ble means hcrcinal'ter described, the spring 29 is held under compression and the door 25 is tightly closed to prevent the escape of air.

lieretotore in terminals of this class much diiliculty has been experienced owing to the great pressure required to cll'ect the release of the door latching means. Ly the use of the devices which I will now describe, however, I have been enabled to obviate these diiiiculties and to provide a door releasing means which can be operated by pressure no greater than that required to propel :1 carrier. The system thus possesses the advantage of being capable of operation with low as well as high pressures. Y

l have also provided a door releasing means which opor independently of the air inlet valve. To these ends I may provide any suitable pneumatic means to lock the latch. in the example shown in Figs. 1 to (3 inclusive, 1 have provided air pressure responsive means in. the form of a diaphragm 5-4, suitably connected witn the lever 51 as by means of a post and a pivotal pin 56. In this example I l' ave provided a housing 5?. having a pair oi" ears to which the lever 51. is iiulcrumed, and into which said lever extends. The weight of the diaphragm 54, the post 55, the pivot 56, and the lever 51, constantly tends to move said lever into its unlatching position. The action of gravity may be assisted by a suitable spring 55) interposed between the top of the post 55 and the under side of the housing 57.

This constant tendency to unlatch or release the door is resisted by air pressure to which the diaphragm 54 is subjected consequent upon the closure or": the door. In

lifting the diaphragm 54 and moving the latching arm 53 into the position shown in Fig. 4, and locking the door in its closed position.

The door should remain looked a sufiicient length of time to insure the discharge of the carrier from the terminal at the other end of the line, whereupon the door 25, at the terminal where the carrier was introduced, should be allowed to open and the air inlet valve 20 should be allowed to close, thereby to restore the parts to their normal condition. The timing of the latch may be effected in various ways. In the example shown in Figs. 1 to 6 inclusive, it is accomplished by venting the chamber 60 to the atmosphere faster than compressed air is supplied thereto through the port 61, this venting of course being suitably timed to allow for the transmission of the carrier. In this example (see Fig. 6) the chamber 60 communicates through one or more, herein a pair of ports 62, with a chamber 63, the latter in turn having means of com munication with the outer atmosphere by a plurality of ports 64 having a combined area greater than that of the port 61. As a means for placing the chamber 63 in communication with the outer atmosphere through the ports 64, I have herein provided a piston valve 65, working in a cylinder 66, and cotiperating with a suitable valve seat 67. The chamber 63 may be, and is herein, formed in the cover plate 38, while the cylinder 66 and valve seat 67 are preferably formed as separate parts secured to the cover plate by a plurality of screws 68.

This construction not only facilitates the manufacturing and initial assembling of the parts, but also permits them to be readily dismounted for the purpose of inspecting and cleaning the piston valve. The lat ter may be seated by the action of gravity alone if desired, but hereinI have provided a suitable spring 69 constantly tending to urge the same toward its seat. One or. more, herein a plurality of ports 7 Q, in the piston portion of the valve 65., providecommunication between the chamber 63 and that portion of the cylinder 66 which is above the piston, so that no air can be trapped in this space to interfere with the proper working of the valve.

The venting valve 65 may be timed by any suitable means, but herein I have provided air pressure responsive means, including a diaphragm 71 having one face eX- posed to the action of atmospheric pressure in a chamber 72, andthe other to a variable pressure in a chamber 73, the latter com municating with the chamber 18 through a passage 74 (see Figs?) and 5). The upper portion of this passage is herein formed bya pipe 75 suitably shaped to prevent the entrance of dirt, water, and oil into the.

passage 74, the upper end of said pipeto this endbeing herein formed with a goose neck or downward bend 76. The eifective area of the passage 74 may be regulated by suitable means, such for example as a needle valve 77 cotiperating with a valve seat 78, for a purpose which will presently appear. The chamber 73 may be placed in communication with the atmosphere through a passage 79 controlled by a valve 80, the latter in turn being carried by a valve stem 81 controlled conjointly with the inlet valve 20 and the door 25.. To this end, the upper end of the valve stem 81 is herein adapted for cotiperation with the lever 45, so that when the inlet valve 20 is opened, as shown in Fig. 4, the venting valve 80 is held to its seat and the passage 79 is closed, but when the valve 20 is closed, the pressure of the lever 45 on the valve stem 81 is removed, and the venting valve 80 can be opened by the air pressure within the chamber 73. This expulsion of the air from the chamber 73 may be ellected by suitable means, such for example as a spring 82 acting in opposition to the pressure in the chamber 73. When, owing to the closing of the door 25 and the opening of the air supply valve 20, compressed air is admitted from the chamber 18 by way of the passage 74 to the chamber 73, since the venting port 79 is then closed by the valve 80, air pressure builds up in the chamber73 and acts against the diaphragm 71 in opposition to the combinded action of atmospheric pressure, and the spring 82, thus forcing the diaphragm toward the right, Figs. 3 and 4.

This movement of the diaphragm may be communicated to the venting valve 65 by any suitable means, as for example, a plunger 88 secured to the diaphragm and having a shoulder or collar 84 normally separatedfrom but adapted to engage the bifurcated depending arm 85 of a lever 86, the latter being fulcrumed on a pivot 87 and adapted to engage a depending stem 88 of the valve 65. When, owing to the opening of the air supply valve 20,,con1pressed air is admitted to the chamber 18, an air pressure is gradually built up in the chamber 73 ata speed determined by adjustment of. the timing valve 77. As the pressure builds up, the diaphragm 71 is forced toward the right (Figs. 3 and 4) and the shoulder 84 at first moves idly, finally bringing up against the lever 86,as shown in Fig.

4. The timeconsumed in the operation to this point provides for the continuance of the air flow for the transmission of the carrier. When however the shoulder 84 brings up against the lever 86 and the latter lifts the venting valve 65, air rushes out of the chamber 60 by way of the passages 62, chamber 63, and ports 64, faster than air is sup plied to said chamber by way of the port 61. As a consequence the diaphragm 54 descends :underthe combined influence of gravity and the spring 59, thus moving the "latch 53 out of engagement with the plate 50, whereupon the cover 25 is free to be opened under the influence'of the spring 32, and the valve 20 is free to be closed under the influence of the spring 2d. The closing of the valve 20 acts through the valve stem 22 to lift the lever 45, thereby releasing the valve stem 81 and allowing the venting valve 80 to be opened by the pressure within the chamber'73, the expulsion of. the air through the passage 79-being effected by movement of the diaphragm? 1 under the influence of the spring 82. This results in the restoration'of the venting valve 65 to its initial position, whereupon the apparatus is in readiness for the introduction of another carrier.

The chambers 72 and 73 are. herein formed within a casing comprising two parts 89 and 90, between which the margin of the diaphragm is clamped by a plurality ofscrews 91. The casing part 89 is herein provided iwith a stem 92 constituting a guide for the hollow plunger 83, and theguide and plungerare chambered toprovide a working'sp'ace'forthe spring 82. The vent port 93 provides'forthe free entrance and exit of air and permits freedom of action of the diaphragm 7 1.

The general operation is as follows: Assuming that the doors 25 at both terminals are open andthe' air supply valves 20 are closed, the operator at one station inserts a carrier in the transittube 11 and'then closes carrier toward its destination. In the mean- ,timetthe a r pressure is communicated to the diaphragm5 1, and the latter acts through the latehfl53 to hold the door 25 in its closed position to'prevent the escape of compressed air at the terminal where the carrier was introduced,andto'lock the inlet valve at such terminal open. The establishment of theair pressure within the'te'rm'inal is effective to.

set'thetimin'g device into operation by the admission of compressed air past the timing valve 77 into the chamber 73. The diaphragm 71 now being forced toward the right (Figs. 3 and 4:) acts through the lever 86 and'venting valve to open the chamber60 to the atmosphere, whereupon air is exhausted-from saidchamber faster than it reeeives airthrough. the "port 61. As a consequence, the diaphragm 54 drops, thus causing the latch 53 to release the cover 25, whereupon the latter opens and in turn releases the inlet valve 20, allowing the latter to close. The valve in closing cuts oil the supply of compressed air, and contemporaneously acts through the lever 415 to release the venting valve 80, whereupon the spring 82 restores the diaphragm 71 to its initial position while expelling the air from the chamber 73, thus restoring the apparatus to its normal condition in readiness for the introduction of another carrier. The carrier is transmitted in the opposite direction by a like operation. It is found in practice that one of the distinct advantages of the apparatus is that the air supply valve closes quickly and thus avoids the objectionable noise which is produced with gradually closing air valves of terminals of this class heretobefore.

Referring now to Figs. 7 to 10, inclusive, I have there shown another terminal embodying my invention, and similar in many respects to that hercinbefore described. In this form, a transit tube 94- entering a termi nal designated generally by the numeral 95 is provided with one or more apertures .90 communicating with a chamber 97 within the terminal. A compressed air supply pipe 98 furnishes a supply of compressed air which is controlled by an air inlet valve 99 coiiperating with a valve seat 100.

A door 101, constituting a closure for the transit tube, is carried by a lever 102, fulcrumed at 103, and is normally held in its open position by a spring 104i encircling a rod 105 pivotally connected at 106 to the lever 102, one end of the spring bearing against an abutment 107 and the other against an abutment 108. In this form, the rod 105 is provided with no stop to limit the opening movement of the door 101, and this arrangement is preferred to that shown in Figs. 3 and 4:, because the door, in opening, is brought to rest by the spring 10 1-, thus avoiding the shock and noise incident to the use of a positive stop. A bolt 109 extending through the door 101 and lever 102, provides a movable connection between them, and a suitable spring 110 interposed between the door and lever insures a tight sealing of the door when in its closed position, and performs a further function hereinafter described.

This terminal is or may be substantially similar to that hereinbefore described. In certain other respects which I will now describe, this terminal differs from the first. In this case a plate 111 carried by the lever 102, is adapted for cooperation with a plunger 112 which carries the air inlet valve 99. The latter is normally maintained in its closed position by a spring 113 encircling the plunger 112 and bearing at one against an abutment 11 1 carried by said plunger, and at its other end against the terminal casing.

Cover lockingmeans, similar to that hereinbeifore described, comprises a lever 115 tulcrumed at 116 and having a latching arm 117 adapted to engage the plate 111 to lock the door 101 in its closed position. The lever 115 is under the control oi air pressure responsive means comprising a dia-' phragm 118connected by a post 119 and pivot 120 with the lever, all similar to the form first described. The upper side 01 the diaphragm is subject to atmospheric pressure within a housing 121, while the under side is subject to pressure within achamber 122 under the control 01 the closure mechanism.

To this end, in this example the plunger 112 constitutes a valve provided with a port 123 cooperating with. a port 124:, the latter communicating with the chamber 122 beneath the diaphragmlll. When, after the introductionoi' the carrier into the transit tube the operator closes the door 101, further depression of the lever 102, permitted by the yielding of the spring 110, causes the plunger 112 to be depressed from the posi tion shown in Fig. 8 until the port 123 communication between the meantime the valve 99 having been opened,

compressed air has been admitted to the chamber 97 and to the transit tube for the propulsion of the carrier. Hence, when communication is established between the chambers 97 and 122 the underside of the diaphragm 108 is subjected to this "pressure and actuates the lever117to'cause the same to lock the lever 101 in its closed position and the air inlet valve 99 in itsopen position. i

Any suitable means may be provided for timing the closingof the air inlet valve and the opening of the cover. In Fig. 9 I have illustrated a simple form of timing means comprising two ports 125 and 126, the first connecting the chambers 97 and 122, and

the second connecting the chamber 122 with the outer atmosphere. everyhas a largercross sectional area than The port 126, howthe port 125, so that after the admission of compressed air to the chamber 122-by way of the ports 123 and 124 by the momentary depression of the plunger112, the

air will flow out of the chamber 122 through the port126 to the atmosphere faster than air is supplied to said chamber through the port 125. It follows that the diaphragm 118 will gradually fall, thus causing the latch to release the door and the inlet valve after a predetermined time. This length of time may be determined by suitably proportioning the ports 125 and 126, as for example, by making said ports in plugs 127 and 128,

reslpectively, screwed into place in the termina Referring to Fig. 10, I have there showna slight modification of the timing means in which aport 126, formed in a plug 127', is controlled by a valve 129 under the influence of a spring 130, which is adapted to yield under the pressure 01 the air and allow its escape past the valve 129 and through a port 131 to the atmosphere. A screw 132, threaded into the plug 127 and provided with. a loclcnut 133, provides a meansto hold the spring 130 under tension. The valve stem may be manually lifted to blow out any accumulation of dust which would tend to lengthen the time period.

While I have herein shown and described two forms or embodiments of my invention for illustrative purposes, and have disclosed and discussed in detail the constructions and to its specific embodiments herein shown,

but that extensive deviations from the illustrated forms or embodiments of the invention may be made without departing from the principles thereof.

Having thus described two embodiments of my invention, what I claim and desire by Letters Patent to secure is: r

1. In a pneumatic despatch tube apparatus, the combination 01" a tube for the trans mission. of carriers, a source of compressed air for the propulsion of carriers through et said tube, a normally open carrier in valve for closing the despatching terminal of said tube, a normally closed air inlet valve for controlling the admission of compressed air to said tube, means for causing said air inlet valve to open when'said carrier inlet valve is closed, apneumatic motor means operated by said motor for locklng said carrier inlet valve closed, and timing means to cause the release ofsaid carrier inlet valve irrespective of the closing of said air inlet valve. i y

2. Ina pneumatic despatch tubeapparatus, the combination of a tube for the transmission of carriers, a source of compressed airfor the propulsion of carriers through said tube, a normally open carrier inlet valve for closing the despatching terminal of said tube, a normally closed air inlet valve for controlling the admission of compressed air to said tube, means for causing said air IIIlB DVZLlVG toopen when sald carrier inlet valve is closed, a pneumatic motor means operated by said motor 'for looking said carrier inlet valve closed, and tim ing means for gradually venting said pneumatic means to cause the releaseof said car- 'r'ier inlet valve. r i

,3, In a pneumatic despatch tube apparaftus,thecombination of a tube for the transmission of carriers, a source, of compressed air. for \the'propulsion of carriers through said tube, a normally open carrier inlet valve for closing the despatehing terminal -of said tube, a normally closed air inlet .valve for. controlling the admission of compressed air to said tube, means for causing said air inlet valve to open when said car- .rier inlet valve is closed, pressure-fluid responsive means operated by said compressed air for. locking said carrier inlet valve closed, ,andtiming means for gradually ventingvsueh compressed air thereby to render said responsive means ineffective to hold said carrier inlet valve closed. 7

In a pneumatic despatch tube apparatus, the combination of a tube for the transvmissionoficarriers, a source of compressed air --forthe propulsion of carriers through said tube, a normally open carrier inlet valve for'closing the despatching terminal ofJsaid tube, a normallyclosed air inlet valve for controllingthe admission of compressed air to said tube, means for causing said air inlet valveto open when said carrier inlet valve is closed, a pneumatic motor means operatedby said motor for locking said carrier inlet valve closed and said air inlet ;valve open,1and timing means for gradually venting said pneumatic means to cause the release of said valves.

5. In a pneumatic despatch tube apparatus,.th e combination of a tube for the transmission of carriers,-a source of compressed airfor thepropulsion of carriers through :said tube, a normally open carrier inlet valve. for closing the despatching terminal of :said tube, a normally closed air inlet valve for controlling the admission of compressed air to said tube, means for causing said air inletvalve to open when said carrier inletvalveis closed, pressure-fluid responsive means operated by said compressed air for locking said carrier inlet valve closed and said air. inlet valve open, and timing means fongradually venting such compressed air thereby to render said responsive means in- -eifective:to maintain said valves thus locked. 1lain-1apneumatic despatch tube apparatus, the combination of a tube for the transmission of carriers, a source of compressed .air for the. propulsion of carriers through said tube, a normally open carrier inlet valve for closing the despatching terminalaof said tube, a normally closed air i inlet valve for. controlling the admission of compressed-air to said tube, means for causung saldalr nlet valve to open when said carrierinletvalve s closed, locking means for ,sai'd valves, pneumatically operated meansconsequent upon the opening of said "air inlet :Valve to'utilize the pressure of said air to cause said locking means to lock said carrier inlet valvein its'closed position and of such air pressure thereby to release said valves and allow said carrier inlet valve to open and said air inlet valve to close.

7. In a pneumatic system, the combination of a source of compressed air, air conducting means having an opening through which compressed air is supplied to said air-eonducting means, a valve for said opening, a latch for locking said valve, compressed. air responsive means to cause said latch to lock said valve, and means operated by an increase of pressure in said air-conducting means for gradually destroying the effect of the compressed air on said latch.

S. In a pneumatic system, the combination of means for furnishing a supply of compressed air, means for utilizing said air for the performance of work, a valve for controlling the supply of compressed air, a latch for locking said valve open, means responsive to the compressed air for causing said latch to lock said valve, and means acting independently of a carrier in transit for gradually reducing the air pressure tending to act through said responsive means to lock said valve.

9. In a pneumatic despateh tube apparatus, the combination with a despatch tube of a terminal therefor having an opening for the carriers, a sealing door for said opening, a latch for said door, pneumatic means to cause said latch to lock said door, a valve to admit air for the propulsion of carriers through said tube, and means distinct from said valve acting independently of a carrier in transit to time the duration of effective locking pressure on said pneumatic means.

10. In a pneumatic dcspatch tube apparatus, the combination with a despatch tube of a terminal therefor having an opening forthe carriers, a sealing door for said opening, a latch for said door, pneumatic means to cause said latch to lock said door, a valve under the control of said door to control the flow of air for the propulsion of carriers through said tube, and means acting independently of a carrier in transit and of said valve to predetermine the duration of effective locking pressure on said pneumatic means.

11. In a pneumatic despatch tube apparatus, the combination with a despatch tube, of a closure therefor, an inlet valve to control the flow of air for the propulsion of carriers through said tube, a lock for said closure, pneumatic means to cause said lock to lock said closure, and means acting independently and in advance of the closing of said inlet valve to cause said lock to release said closure a substantially predetermined time after the opening of said inlet valve and before the closure of said inlet valve.

12. In a pneumatic despatch tube apparatus, the combination with a despatch tube, of a closure therefor, a manually operated inlet valve to control the flow of air for the propulsion of carriers through said tube, a lock for said closure, pneumatic means to cause said lock to lock said closure, and means acting directly to cause said lock to release said closure a substantially predetermined time after the opening of said inlet valve and before the closure of said inlet valve.

13. In a pneumatic despatch tube apparatus, the combination with a despatch tube and means for supplying compressed air thereto, of an inlet valve controlling the supply of compressed air to said tube, a closure for said tube, locking means for said closure, means responsive to said compressed air to operate said locking means to lock said closure in its closed position and said valve in its open position, timing means to destroy effective pressure on said responsive means after a determined period of time, and means operated by said locking means for holding said inlet valve open until after the lapse of said determined period of time.

In testimony whereof, I have signed my name to this s )ecification.

AMES Gr. MACLAREN.

It is hereby certified that in Letters Patent No. 1,367,163, granted February 1, 1921, upon the application of James G. Maclaren, of Marnaroneck, New York, for

an improvement in Pneumatic-Despatch-Tube Apparatus, an error appears in the printed specification requiring correction as follows: Page 7, line 8, claim 12,

strike out the words acting directly and insert the Words acting independently and in advance of the closing of said inlet valve; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 15th day of March, A. D., 1921.

i M. H. COULSTON,

Commissioner of Patents.

[SEAL 

